The present invention relates to a method of extracting fiber flocks from textile fiber bales, and to a control arrangement for controlling the operation of a machine which performs such extraction.
There are already known various methods of extracting fiber flocks from textile fiber bales by means of an extracting member movable in a plurality of passes over and lowerable onto the bales to extract the fiber flocks from the upper bale surfaces with a penetration depth into the bales that is variably dependent on the bale height and to deliver the extracted fiber flocks to a flock transportation means, as well as arrangements for controlling the operation of correspondingly constructed machines for extracting fiber flocks from textile fiber bales. A machine of this kind typically includes a reciprocating raising and lowering device movable back and forth along the bales, and an extracting member mounted on the reciprocating device for up and down movement therewith and including a rotatable extracting roller operative to deliver fiber flocks extracted from the bales to flock transportation means.
A control arrangement of the above type is disclosed, for instance, in the German published patent application DT-OS No. 32 45 506. The machine controlled by this control arrangement travels back and forth along a straight-line trajectory above a group of textile fiber bales and, in the course of such movement, a rotating extraction roller mounted on the machine extracts fiber flocks from the bales. The extracting roller can penetrate into the surface region of the respective bale with a varying force which can be adjusted to take into account the varying bale heights and thus the varying bale densities. For this purpose, there are provided three switches which are arranged with adjustable mutual spacing along a vertical line. During the processing of the bales, these switches are sequentially operated as the extraction member is lowered. Each of the switches controls a pneumatic switching valve which opens the path for the flow of pressurized air at a predetermined pressure into a pressure air cylinder-and-piston unit. The piston rod of this unit is connected to a middle portion of a length of cable. The cable length passes, to either side of this middle portion, around respective guide rollers. The extraction member is connected to a cable end portion which depends from one of the guide rollers, while a counterweight which compensates for the weight of the extraction member is secured to the other end portion of the cable.
An important disadvantage of this particular construction of the above-mentioned arrangement is that the cable can not exert pressure on the extraction member and thus on the bale. Accordingly, this publication merely teaches the control of the pressure of the extraction member on the bale surface by means of switches and the associated supply of pressurized air to the pressure cylinder-and-piston unit, with a varying pressure depending on the bale height.
In use of this particular control system, the extraction member extracts flocks from the uppermost bale layer with a predetermined constant pressure which is controlled by the upper switch, until the middle bale layer is reached. At the beginning of extraction of fiber flocks from this middle layer, the middle one of the switches causes the pressure delivered to the pressure cylinder-and-piston unit to rise relatively to the pressure supplied to the cylinder-and-piston unit previously, for processing the middle layer. Finally, when the lower bale layer is reached, the lower switch causes a constant pressure that is lower than that used before to be delivered to the cylinder-and-piston unit for the processing of the lower bale layer.
One disadvantage of this control system is that, upon transfer from one layer to the next, the effective pressure is changed in a stepwise manner, which results in a correspondingly stepwise variation of the processing performance. Another disadvantage of this approach is that only one bale group, with all of the bales of this group being of the same height, can be processed; otherwise, the switch positions would have to be constantly adapted to the changing bale heights.